CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Programming & Development

Parallel version of Ax=b ???

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   March 29, 2011, 17:13
Default Parallel version of Ax=b ???
  #1
pkr
Member
 
Join Date: Nov 2010
Posts: 33
Rep Power: 5
pkr is an unknown quantity at this point
I am trying to understand the way Ax=b is solved in parallel across the processors.

The original mesh is comprised of 5 cells. The original matrix A without any decomposition is:
-4 0 4 0 0
0 -3 0 0 3
4 0 -8 9 0
0 0 9 -6 5
0 3 0 5 -7

After using decomposePar utility the matrix A is decomposed in two smaller matrices as follows:
First matrix
========
-3 0 3
0 -6 5
3 5 -7

Second Matrix
==========
-4 4
4 8


When PCG solver is invoked, each process solves Ax=b independently and exchanges some information with other process to ensure correctness.

My queries are as follows:

1. What is being exchanged? I see that in every iteration during Amul, some parts of vector pA is being sent to neighboring process. The neighboring process receives pA and performs additional computation to rectify wA.

wA[] -= coeffs[] * pA_received[];

2. Where do the coefficients come from? What's the significance of coeffs?

3. How does subtracting "coeffs[] * pA_received[]" from wA[] leads to the correct solution mathematically?


Thanks in Advance.
pkr is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Superlinear speedup in OpenFOAM 13 msrinath80 OpenFOAM Running, Solving & CFD 18 March 3, 2015 06:36
Saving *.cas and *.dat from parallel version Pfalcon ANSYS 1 August 15, 2009 08:18
Saving *.cas and *.dat from Fluent parallel version Pfalcon FLUENT 2 August 14, 2009 14:57
UDF in parallel version of fluent yobee FLUENT 2 August 5, 2004 00:36
Parallel version of SIP ? Ravikanth Avancha Main CFD Forum 1 March 19, 1999 15:21


All times are GMT -4. The time now is 17:07.